Sunday, August 13, 2017

The two major dinosaur news stories since Borealopelta have been the giant titanosaur Patagotitan and a shake-up in troodontid dinosaurs that, among other things, puts another stake into Troodon formosus. For some relevant thoughts on Patagotitan, I direct you to "On this occasion of receiving a new giant dinosaur" from a few years back. I'd instead like to spend some time on the dark and subtle art of taxonomy and how it relates to old names based on poor material.

Sunday, August 6, 2017

At last, the "Suncor ankylosaur" takes its place among the described! With the description of Borealopelta, I can cross off one more from "Coming Attractions". (That's four and a half down, with half-credit on Daspletosaurus, and eighteen and a half to go.) The first thing I recommend that you do is to download the description and the supplemental information from here.

Sunday, July 30, 2017

To be perfectly honest, we use simplifications for practically everything. Atoms don't really look like bunches of colorful spheres surrounded by smaller spheres orbiting them. The Earth is an oblate spheroid, which is close to but not quite a sphere. The planets of the Solar System don't have nice circular orbits centered on the center of the sun, lying in a flat plane. The need to simplify complex topics is obvious, both on the grounds of providing what someone needs to know to do something, and tailoring material to what someone can understand. There's a simple version for grade school kids, a more complex version for undergrads, and so on, until you're working professionally, where you've got very detailed models which are still abstractions, only closer (hopefully) to reality. One of these simplifications in geology is "geological formations as layer cakes", where formations maintain their thicknesses and are easily distinguished. The layer cake abstraction is most useful at a local level, in settings where deposition wasn't switching back and forth between different processes and sediment sources. For example, the Ordovician rocks of the Twin Cities fit pretty well. However, the cake starts getting funny-looking as you head into southeastern Minnesota. The photo below is of the Sogn roadcut, where some familiar rocks are exposed.

No, I don't know how to pronounce "Sogn".

At Sogn, though, what we would know as the lower half of the Platteville Formation is absent. Instead, the deposition of the Glenwood Formation persisted much longer (Sloan et al. 1987). Similarly, the Decorah Shale is at its thickest at the Brickyard in Lilydale, but going southeast, the upper part is replaced by the Cummingsville Formation. We can get these shifts in deposition from a number of causes. Sometimes you're looking at the boundary between two different modes of deposition shifting over time (such as a shoreline prograding or regressing). Sometimes there is a tectonic component, such as a basin subsiding. Sometimes the source of sediment changes or runs out.

Here's a more advanced example: the interval long known as the Franconia Formation and now known as the Tunnel City Group is divided into four parts in the St. Croix Valley. These are the Mazomanie Formation and three members of the Lone Rock Formation, from oldest to youngest the Birkmose, Tomah, and Reno members. We've met the Mazomanie Formationbefore; it's a quartz-rich light-colored very-fine- to medium-grained sandstone with abundant burrows and various forms of cross-bedding. (This of course is also a simplification, boiling down the essence of a rock unit that was deposited across some hundreds of thousands of years over parts of two states.) The Lone Rock Formation is a finer-grained, darker, wormier unit. The Birkmose Member is a greenish-gray very-fine to fine-grained sandstone, with a lot of feldspar and glauconite grains (glauconite being a green mineral that likes to form on marine bottoms with little sedimentation). The Tomah Member is a brownish-gray feldspar-rich siltstone and very-fine-grained sandstone with thin interbeds of gray-green shale. Finally, the Reno Member is similar to the Birkmose Member, but somewhat finer-grained and with better defined sedimentary structures. The Mazomanie Formation is a lateral equivalent to most of the Lone Rock Formation. While the Lone Rock Formation was deposited in an offshore setting centered in Minnesota, the Mazomanie was deposited under shallower conditions, and its sediment came from topographic highs to the north and east in central Wisconsin. The two formations intertongue over a wide geographic and vertical range. If you trace the zone of intertonguing, you're seeing deposition fluctuating over time, as pulses of uplift and erosion on the Wisconsin highs sent sand to the south and west. It doesn't look much like a layer cake, at least not a competent example. There are at least three major Mazomanie tongues, plus who-knows-what going on between Franconia and Marine-on-St. Croix. The Tomah seems to go quietly, but the Reno is engaged in some kind of geological close-quarters combat with the Mazomanie.

Schematic colorized version of St. Croix diagram in Berg (1951, 1954), with information from Quaschnick (1959) taken into account for northern Tomah extent. Thick black lines are
reasonably certain stratigraphic contacts, thin black lines are inferred, red line are
biostratigraphic boundaries, and brown vertical lines show the extent of the
measured sections (with the locations identified below the lines). With Berg's Woodhill Member removed (Ironton Sandstone Member of the Wonewoc Sandstone), the Tunnel City Group here is around 52 m (170 ft thick). The rocks continue for a long way south of Afton, but there aren't any good outcrops for a while.

The concept of a simple planar formational contact is in itself a simplification. Sometime you get a nice flat contact between two units. Sometimes you get a contact with vertical relief, because the underlying formation was eroded into hills and valleys before the overlying unit was deposited. Sometimes the contact is arbitrary, because the lower rock type grades into the upper rock type. Sometimes the contact is arbitrary because the two units meet over a zone of alternating beds, due to the two types of deposition switching from time to time. This last kind is what we're seeing here between the Mazomanie and the Lone Rock formations, and if we could see through the ground to get a full picture of what is going on from Taylors Falls from Afton, the contacts would probably look "fuzzy" due to smaller and smaller-scale interbedding.

Finally, I've mentioned a few times how the Franconia Formation was problematic because of mixing rocks with biostratigraphy. Back in the day, people tried to define subunits based on trilobites. Berg (1951, 1954) pointed out that the zones don't actually follow the rocks. When your biostratigraphic formations don't correspond to rock types, it
makes it a real pain to try to map. In addition, you have to have both a
paleontologist who can identify the relevant species, and well-preserved examples of those species in the rocks you are studying. (Of
course, it gets even worse if some significant number of the species you
are dealing with are actually minute variations on a single species,
but who would ever do that to you?) The red lines in the diagram show that the trilobite zones skew upward going north in the St. Croix Valley. This is not entirely surprising, when you get down to it: the Lone Rock Formation is notable for its glauconite content, which as mentioned is a sign of low sedimentation rate. The Mazomanie Formation lacks glauconite. I'm going to guess that the Mazomanie had a greater rate of sedimentation than the Lone Rock, which would naturally cause the zone boundaries to skew higher where there is more Mazomanie deposition.

Sunday, July 16, 2017

Here's a little more information on a few enigmas from previous posts, with some additional photos from the University of Minnesota paleontological collections. First up is Pipestone National Monument's "Lingula calumet", then Scenella, and finally Cylindrocoelia minnesotensis.

Sunday, June 25, 2017

Investigating the rocks of Saint Croix National Scenic Riverway (SACN) is a tougher nut than working in MNRRA. Most of the area where rocks are exposed in MNRRA is part of some kind of park (city, state, regional, county, etc.) and generally accessible to the public. Much of the area with outcrops on the St. Croix is private land, and many of the key localities in the literature are now overgrown, destroyed by construction, or are roadcuts next to busy highways. Determining where you are in the strat column is also more difficult. In MNRRA, it's hard to get mixed up if you can tell sandstone from limestone/dolomite and shale. In SACN, you're dealing with several quartz-rich medium to coarse sandstones that tend to look the same, with some intervening shaly, dolomitic, or finer-grained sandy formations, and in the literature practically every single investigator had their own preferred system of names right up until the 1960s. Finally, in MNRRA there are abundant and diverse fossils in the Platteville and Decorah, while in SACN the special of the day is the BLT (burrows, lophophorates [brachiopods and hyoliths], and trilobites) with a side order of mystery snails, and you have to work for everything but the B.

Sunday, June 11, 2017

With the recent coverage of Zuul and the Suncor nodosaur, it seems like a good time for another entry on North American armored dinosaurs. We've already visited with Nodosaurus textilis, Stegopelta landerensis, and Hierosaurus sternbergii. Today's star is another species of similar vintage, Hoplitosaurus marshi. Like our other three subjects, Hoplitosaurus was initially described around the turn of the 20th century from a single armor-heavy specimen found in Cretaceous rocks of the American West. Also like the other three, Hoplitosaurus received barely a blurb for its initial description and had to wait for someone else to spare a little more time and ink.

The part and counterpart of University of Minnesota Paleontology Collections 4090, holotype of graptolite Dictyonema minnesotense Ruedemann 1933, collected from the St. Lawrence Formation at a no-longer extant site in Afton, Minnesota, now within Saint Croix National Scenic Riverway.

Tuesday, May 23, 2017

Some recent events have provided photographic fodder for a brief unscheduled revisit of safety concerns in the rocks of the Twin Cities, but first I am going to plug the reborn Park Paleontology newsletter. I'll hit it some more this weekend in more detail, but I particularly want to call out Chapter 3 by Emily Thorpe, who was a Geoscientists in the Parks intern over the winter at Salinas Pueblo Missions National Monument. Among other discoveries, she's got the first vertebrate from the Yeso Group (Arroyo de Alamillo Formation), the part and counterpart articulated back half of a skeleton. We've had a lot of great projects from GIPs the past few years, and I'd strongly encourage college students in the geosciences to have a look when the next batch of positions comes out.

Meanwhile, back in the Ordovician...

You may remember the following photo from this post, or this post. Coincidentally, in both posts the photo is being used as an example of a hazard. It was taken back in June 2013 along the road into Crosby Farm Regional Park, before you get to Watergate Marina.

I wonder where this is going...

If you take that road today (May 2017), this is what you'll see:

...the answer appears to be "down".

This is why you should not stand too close to the walls of the bluffs, or to the edge on top.

Meanwhile, over at Shadow Falls, the Decorah Shale presents a different issue, one that can be expressed as a recipe titled "Reconstituted Ordovician Seafloor": take a hillslope of weathered marine shale, and over the course of six days add nearly five inches of rain. It's amazing!

Hiking boots? More like cleats.

The running water is Nature's subtle way of telling you to stay off.

It's not the mud itself that's the big problem (unless you hate mud, in which case you're really in the wrong place), but the slippery sloppy footing. If you go over into the ravine, it's not going to be easy to get you out!

Sunday, May 14, 2017

As promised earlier, I've reworked the skeletal anatomy section of the old website and added it here. I have rewritten parts of it, particularly to improve the section covering vertebrae, and have substituted different skull figures. I also strongly encourage you, if you have not done so already, to marvel in some armored dinosaurs, the ankylosaurid Zuulcrurivastator, and the unnamed Suncornodosaurid. (Also, that's a heck of a plesiosaur that the Tyrrell has to go with the nodosaur!)

Sunday, May 7, 2017

Three new sauropod species were published this week, although technically speaking all three are based on fossils that have been mentioned in the literature previously. This is just how things work in paleontology. Even if you know you have something new, it may be years or even decades for a description to surface. The three sauropods of the week cover three continents, two epochs, and three lineages. In a slight upset none of them are South American titanosaurs. Instead, they are diplodocid Galeamopus pabsti from the Upper Jurassic Morrison Formation of the United States, titanosaur Tengrisaurus starkovi from the Lower Cretaceous Murtoi Formation of Russia, and brachiosaurid Vouivria damparisensis from the Upper Jurassic Calcaires de Clerval Formation of France.

Sunday, April 30, 2017

One of the projects I'm working on concerns the paleontology and geology of Saint Croix National Scenic Riverway, so I've been doing some location scouting to get a feel for the geology. It's not quite as simple as MNRRA, even though I'm still only dealing with a handful of formations and there's not much structural geology to contend with. The main issue is finding access to outcrops. Other complications include sparser fossils and all of these darn Cambrian cratonic sheet sandstones that look about the same.

Sunday, April 16, 2017

I apologize for having been light on the whole "Minnesota" and "invertebrates" part of the blog for this year. Having been doing this for a few years now, the low-hanging fruit is picked, and of course the winter is not the best time to be out and about in the rocks, even if "winter" came with quotation marks instead of snow this year. I'm currently on a short trip to Reston, Virginia, to do some work at the USGS, but I thought I'd at least try to put in something relevant for those topics. Then, of course, there’s a sauropod.

Sunday, April 9, 2017

Although Keating, Featherstonhaugh, and Nicollet made significant contributions to Minnesota geology, the first true geological survey in what is now Minnesota would have to wait until 1847. At this point, the future state was split between Wisconsin Territory and a leftover chunk of Iowa Territory, and with the pending organization of Wisconsin into a state it was actually touch-and-go for a while how the boundaries would fall out. The convergence of St. Croix Valley interests versus the rest of Wisconsin with the old Northwest Territory stipulation that a maximum of five states be made out of the territory, and a dash of underlying slave state versus free state politics, could have led to anything from a super-Wisconsin incorporating much of what is eastern Minnesota to a separate state centered on the St. Croix Valley with Stillwater as the capital (the story can looked at briefly here). Anyway, in 1847 Congress authorized a geological survey in Minnesota and neighboring areas, and appointed David Dale Owen to conduct the work (Hendrickson 1945).

Sunday, April 2, 2017

Having done a relatively large number of dinosaur-related posts in the past few months, I've found myself running into anatomy and anatomical terms of location (dorsal, lateral, etc.). Given that not everyone knows all about the jargon, parenthetical glosses tend to slow things down, and I had perfectly serviceable glossaries for these subjects on the late Thescelosaurus!, I decided to revisit that information. I've started by putting the anatomical terms of location on their own separate page. Wikipedia has a useful summary as well, but if you aren't a wiki fan, like having the information on hand here, or just like diagrams featuring the excellent Wild Safari Sauropelta, this is for you. Eventually, I plan to put up skeletal anatomy as a page, and probably a geologic time scale as well (or at least a link to one).

Sunday, March 26, 2017

If you are the kind of person who reads a blog like this, you've probably already heard the news about a new analysis (Baron et al. 2017) finding that sauropodomorphs and theropods may not be the closest of evolutionary siblings, as we've long believed. Instead, theropods were paired with ornithischians, and Sauropodomorpha got to pair with the herrerasaurids in the settlement. For the new alliance of bitey (theropod) and beaky (ornithischian) dinosaurs, the authors went back into the mists of time and pulled out Ornithoscelida, a name first proposed by Thomas Henry Huxley for a roughly similar grouping of dinosaurs. There has already been a lotofdiscussion about the publication, and apart from some criticisms of the exclusion of certain forms and how names were redefined, the tone at this moment is open-minded.

The idea that the relationships of the three major lineages of (non-avian, or "classic") dinosaurs are not what we thought them to be is not far-fetched. The earliest theropods, sauropodomorphs, and ornithischians all had the same grandparents, so to speak. Unsurprisingly these early forms all look kind of similar, had similar lifestyles, and thus are liable to be mixed up by later observers, especially when the observation is happening 230 million years later and the subjects have been reduced to skeletons. (It's a common problem for species near the base of branching lineages to be difficult to place.) Going from (S+T)+O to S+(T+O) does require some rethinking on how and when certain features appeared. It also throws a bit of a kink into the branch-swapping basal saurischians: Eoraptor, herrerasaurids, and friends. Eoraptor had seemed reasonably comfy among the sauropodomorphs and herrerasaurids with the theropods, and here they are switching places.

There is also an interesting question concerning the origin of ornithischians. Historically, Triassic ornithischians have been a problem due to their frustrating insistence on not being there. After a few decades of redating various formations and reassessing a bunch of teeth, we're down to Pisanosaurus (which is itself attracting questions) and Eocursor. Woo-wee. Under the traditional Saurischia–Ornithischia split, there should be more Triassic ornithischians, because of the record of Triassic saurischians. Pairing ornithischians with theropods has the potential to resolve this if it should turn out that ornithischians and theropods actually branched later in the Triassic (which also results in some "theropods" becoming basal ornithoscelidans, but it's not as if current basal theropods haven't been living under taxonomic instability). The results of the current study don't support this, but you never know. (In fact, the authors find that ghost lineages may go back all the way to nearly the beginning of the Triassic, because Nyasasaurus has suddenly started acting like a massospondylid, but then again the rocks it came from may be younger than currently thought.)

At any rate, an injection of controversy is good for the field. Either other studies support the authors, in which case we learned something new, or they don't, in which case the authors got people looking at dinosaur relationships and evolution from new angles, which is also good. In fact, now that I'm thinking about it, it's kind of odd that we have as much consensus as we do. Off the top of my head, for persistent trouble spots we've got Triassic groups and species that can't seem to make up their minds about where they belong, megaraptorans as carnosaurs or coelurosaurs, the knot of undecideds where Dromaeosauridae, Troodontidae, and birds meet, and what to do with various "hypsilophodonts". This doesn't count a few other areas that are questionable because of lack of attention, like the Box of Mystery that is Titanosauria.

All that said, I *am* going to let the issue sit before, say, updating The Compact Thescelosaurus; publications find things all the time that are not supported by later analysis (hey, Phytodinosauria, the hip alternative of the '80s and '90s). Also, redefining Saurischia to hold just sauropodomorphs and herrerasaurs was a mis-step. Just let herrerasaurs into Club Sauropodomorpha, let Saurischia go into dignified retirement, and call it a day.

Sunday, March 12, 2017

Two dinosaurs were published on February 16, 2017. One of them was Isaberrysaura mollensis, which has gotten a lot of press because it's a weird basal ornithischian with gut contents. The other was Xingxiulong chengi, which hasn't gotten as much attention, although the Wikipedia article is pretty extensive. Xingxiulong is among what we used to call "prosauropods", now known as basal sauropodomorphs. It is represented by most of the skeleton, excepting the tips of the jaws, most of the hands, and the coracoids and sternal elements. It also provides me a half-point on my prediction for "prosauropods", which I'll take because it's been kind of a slow year so far.

Sunday, March 5, 2017

Judging by place names, Joseph Nicollet must have been a much more popular man than George William Featherstonhaugh. (Or maybe it was just the fact that it took sixteen letters to spell George's name while only taking seven to say it that proved unappealing.) I'm not sure if anyone in Minnesota attached George's name to anything, whereas Nicollet is the namesake for such pieces of geography as Nicollet County, Nicollet Mall, and Nicollet Island. His name was even attached to a ballpark, the long-time home of the old Minneapolis Millers, although probably the adjacent Nicollet Avenue was the main inspiration.

Sunday, February 26, 2017

Washington, D.C. is not generally ranked in the first order of fossiliferous areas. It can hardly be considered a bust, though. The "Middle" Cretaceous Potomac Group (due to a tragic geologic oversight, there is no formal Middle Cretaceous) has been reasonably kind for plants; see Fontaine (1889, 1896), Knowlton (1889), Ward (1895), Ward et al. (1905), and Sinnott and Bartlett (1916) for some of the gory details. Something you may notice from that list is that all of those publications are at least a century old. The obvious problem is that Washington is a city first and foremost, so it's not like there are a lot of outcrops for prospecting any more. The Potomac Group has also produced some scrappy dinosaur remains, and anywhere that the Potomac River once flowed is liable to have cobbles with Skolithos tubes, eroded from Cambrian rocks up in the mountains. The classic Potomac Skolithos cobbles are rounded pieces of orangeish quartzite with simple vertical Skolithos burrows, similar to skinny pencils and with a tendency to stand out from the host rock. Washington is also blessed with a profusion of fossiliferous building stone, particularly the inevitable "Indiana Limestone" (Salem Limestone). But I digress. In a city, we cannot come to the outcrop, so the outcrop must come to us. This is where subsurface explorations come in handy. We talked about taking cores from lake sediments a few weeks ago. The subsurface of Washington, like any major city, has been picked at innumerable times, uncovering fossils from places such as just north of the White House and near the Washington Monument.

Sunday, February 19, 2017

This week saw the publication of two new dinosaurs. Both of them have something to recommend them, but given my own preoccupations we'll have to leave Xingxiulong for someone else, or for another time. (Feel free to hop over to the paper, though!) Instead, we shall meet Isaberrysaura mollensis, a basal ornithischian packing an identity crisis and a belly full of seeds.

Saturday, February 11, 2017

I've been looking at some of the early geological expeditions in the United States for work, and I thought I'd take a couple of posts to look at some of the pre-Civil War geologists who visited the Twin Cities area of Minnesota. We've already briefly looked at William Keating and the Stephen Long expedition of 1823, so I thought I'd move on to the next figure of note, George William Featherstonhaugh.

George William Featherstonhaugh, borrowed from Wikimedia Commons, who borrowed it from the Minnesota Historical Society.

Sunday, January 29, 2017

As we've seen from time to time with packrat middens, there are many ways of looking at past ecological conditions. A common method in more humid environments that the deserts and mountains of the Southwest is studying lake deposits, which is quite well-suited to the Land of 10,000 Lakes. Many types of paleoecologically useful fossils can be extracted from lake sediments, ranging from diatoms ("algae" with silica cell walls), to spores and pollen, to mollusks, to ostracodes, to the jaw parts of certain midge larvae. (There are, of course, other kinds of fossils that can be found in lakes, but they aren't as commonly used for paleoecological work. A single mammoth, while certainly of great interest, is not as versatile for this kind of thing as innumerable pollen grains spread over thousands of years.) Spores and pollen are part of a group of fossils known as palynomorphs, organic-walled microfossils. There are several other types of palynomorphs, including various cysts and so forth, but for the purposes of upper Pleistocene and Holocene lake sediments in Minnesota, spores and pollen are clearly the stars of the show.

Sunday, January 22, 2017

A couple of new publications concerning mammoths in National Park Service units have crossed my desk recently, so it seemed like a good opportunity to say a few further words on behalf of extinct proboscideans in the National Parks. I present to you first the finely wrought map below, which shows the various parks where body fossils of mammoths, mastodons, and their friends have been reported. At press time, there were 37 parks, monuments, and so forth with confirmed records, and another six with possible records (cases where the locality is not clear). This map has the novelty of differently colored and shaped symbols, which aside from providing a splash of color, show a preponderance of mastodons in the northeast and mammoths in the southwest. I've relied on the literature and such, so there's definitely the chance that some of the "mammoths" are mastodons, and vice-versa. Most of these records are from the Pleistocene, but there are a few that are older; notably, John Day Fossil Beds National Monument and Niobrara National Scenic River have both gomphotheres and mastodons of pre-Pleistocene age. The great majority of the mammoth reports in the lower 48 are likely Columbian mammoths, Mammuthus columbi (M. exilis of Channel Islands National Park being a notable exception), but given the ambiguities in North American mammoth taxonomy, I figured it wasn't worth the time to try to split them up.

Sunday, January 15, 2017

Sorry, but I don't seem to have a better picture of local hyoliths, unless the things mentioned in this post or this post are hyoliths.

This week, the big paleontological news had nothing to do with dinosaurs, or mammals, or anything with bones at all for that matter. Instead, hyoliths got to be the subject of dozens of news articles, for the happy reason that their relationships are no longer quite so enigmatic. Undergrad Joseph Moysiuk of the University of Toronto and colleagues have presented research on the little guys showing that they were equipped with a tentacle-laden feeding apparatus, making them next cousins to...

Sunday, January 8, 2017

Making predictions about paleontology is kind of awkward, at least if your predictions are based on what is published. Because there's usually five to ten years between a discovery and its publication, there's often a sense of what is out there, just not when it will appear. After all, we've got abstracts, press releases, photos on social media, etc... But what the hey? We're just having fun (hopefully). Lots of links to names are included in case you're mostly here for the Ordovician and aren't familiar with the lingo. Below are my predictions for dinosaur paleontology in the year 2017, after the photo of actual dinosaurs taken at much expense and personal risk via a secret and unfortunately now-lost technology.

Actual photo from the late Campanian of Canada. Things were surprisingly geometric then. Note that dinosaurs in their natural environment kind of hang around as if they are on coffee break, instead of constantly being on murderous rampages.